bug 1074917 - teach atk to get states from proxies r=surkov, davidb, mrbkap

We need to implement things like
https://developer.gnome.org/atk/unstable/AtkObject.html#atk-object-ref-state-set
and the same basic thing on windows.  That API is fundamentally sync,
but the information necessary to implement it is only available in the
child process.  That seems to leave us with two options, either we can
use sync ipc or we can use async ipc but spin a nested event loop.  If
we were to spin nested event loops we'd have to be careful to make sure
a11y didn't do anything until the nested event loop was done, and then
a11y would have to deal with whatever changed.  I'm not sure that will
work, and since the system is probably waiting for the accessibility
information anyway I don't think we get much out of spinning the event
loop.  So I think its somewhat less bad to use sync ipc here.

accessible/atk/AccessibleWrap.cpp

@@ -892,19 +892,18 @@ TranslateStates(uint64_t aState, AtkStateSet* aStateSet)
 AtkStateSet *
 refStateSetCB(AtkObject *aAtkObj)
 {
-    AtkStateSet *state_set = nullptr;
-    state_set = ATK_OBJECT_CLASS(parent_class)->ref_state_set(aAtkObj);
+  AtkStateSet *state_set = nullptr;
+  state_set = ATK_OBJECT_CLASS(parent_class)->ref_state_set(aAtkObj);
 
-    AccessibleWrap* accWrap = GetAccessibleWrap(aAtkObj);
-    if (!accWrap) {
-        TranslateStates(states::DEFUNCT, state_set);
-        return state_set;
-    }
-
-    // Map states
+  AccessibleWrap* accWrap = GetAccessibleWrap(aAtkObj);
+  if (accWrap)
     TranslateStates(accWrap->State(), state_set);
+  else if (ProxyAccessible* proxy = GetProxy(aAtkObj))
+    TranslateStates(proxy->State(), state_set);
+  else
+    TranslateStates(states::DEFUNCT, state_set);
 
-    return state_set;
+  return state_set;
 }
 
 static void

accessible/ipc/DocAccessibleChild.cpp

@@ -36,5 +36,19 @@ DocAccessibleChild::ShowEvent(AccShowEvent* aShowEvent)
   SerializeTree(aShowEvent->GetAccessible(), data.NewTree());
   SendShowEvent(data);
 }
+
+bool
+DocAccessibleChild::RecvState(const uint64_t& aID, uint64_t* aState)
+{
+  Accessible* acc = mDoc->GetAccessibleByUniqueID((void*)aID);
+  if (!acc) {
+    *aState = states::DEFUNCT;
+    return true;
+  }
+
+  *aState = acc->State();
+
+  return true;
+}
 }
 }

accessible/ipc/DocAccessibleChild.h

@@ -33,6 +33,11 @@ public:
 
   void ShowEvent(AccShowEvent* aShowEvent);
 
+  /*
+   * Return the state for the accessible with given ID.
+   */
+  virtual bool RecvState(const uint64_t& aID, uint64_t* aState) MOZ_OVERRIDE;
+
 private:
   DocAccessible* mDoc;
 };

accessible/ipc/PDocAccessible.ipdl

@@ -24,7 +24,7 @@ struct ShowEventData
   AccessibleData[] NewTree;
 };
 
-protocol PDocAccessible
+prio(normal upto high) sync protocol PDocAccessible
 {
   manager PContent;
 
@@ -38,6 +38,9 @@ parent:
   Event(uint32_t type);
   ShowEvent(ShowEventData data);
   HideEvent(uint64_t aRootID);
+
+child:
+  prio(high) sync State(uint64_t aID) returns(uint64_t states);
 };
 
 }

accessible/ipc/ProxyAccessible.cpp

@@ -6,6 +6,7 @@
 
 #include "ProxyAccessible.h"
 #include "DocAccessibleParent.h"
+#include "mozilla/unused.h"
 #include "mozilla/a11y/Platform.h"
 
 namespace mozilla {
@@ -38,5 +39,13 @@ ProxyAccessible::SetChildDoc(DocAccessibleParent* aParent)
     mOuterDoc = false;
   }
 }
+
+uint64_t
+ProxyAccessible::State() const
+{
+  uint64_t state = 0;
+  unused << mDoc->SendState(mID, &state);
+  return state;
+}
 }
 }

accessible/ipc/ProxyAccessible.h

@@ -54,6 +54,11 @@ public:
    */
   role Role() const { return mRole; }
 
+  /*
+   * Return the states for the proxied accessible.
+   */
+  uint64_t State() const;
+
   /**
    * Allow the platform to store a pointers worth of data on us.
    */